Publications by authors named "Benjamin J Frisch"

19 Publications

  • Page 1 of 1

Hematopoietic Stem Cell Cultures and Assays.

Methods Mol Biol 2021 ;2230:467-477

Department of Pathology and Laboratory Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA.

The adult hematopoietic system is repopulated in its entirety from a rare cell type known as hematopoietic stem cells (HSCs) that reside in the marrow space throughout the skeletal system. Here we describe the isolation and identification of HSCs both phenotypically and functionally.
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http://dx.doi.org/10.1007/978-1-0716-1028-2_30DOI Listing
January 2021

Acute and late effects of combined internal and external radiation exposures on the hematopoietic system.

Int J Radiat Biol 2019 11 30;95(11):1447-1461. Epub 2019 Jul 30.

Department of Pediatrics, University of Rochester Medical Center, Rochester, NY, USA.

Incidents, such as nuclear facility accidents and the release of a 'dirty bomb', might result in not only external irradiation of personnel, but additional internal exposures through concomitant inhalation and/or ingestion of radioactive particulates. The purpose of this study was to define the impact of such a combination of radiation injuries on the hematopoietic niche. To assess changes in the murine hematopoietic system, we used a combined exposure of total body irradiation (TBI, 6 Gy) followed immediately by an internal (intraperitoneal) administration of 100 Ci of soluble Cs. We then evaluated acute survival in combined versus single modality exposure groups, as well as assessing hematopoietic function at 12 and 26 week time points. Acutely, the combination of external and internal exposures led to an unexpected delay in excretion of Cs, increasing the absorbed dose in the combined exposure group and leading to mortality from an acute hematopoietic syndrome. At 12 weeks, all exposure paradigms resulted in decreased numbers of phenotypic hematopoietic stem cells (HSCs), particularly the short-term HSCs (ST-HSC); long-term HSCs (LT-HSC) were depleted only in the internal and combined exposure groups. At 26 weeks, there was significant anemia in both the TBI alone and combined exposure groups. There were decreased numbers in both the LT- and ST-HSCs and decreased functionality, as measured by competitive repopulation, was seen in all radiation groups, with the greatest effects seen in the internal and combined exposure groups. Our data indicate that a combined injury of sublethal external irradiation with internal contamination induces significant and persistent changes in the hematopoietic system, as may have been predicted from the literature and our own group's findings. However, a novel observation was that the combined exposure led to an alteration in the excretion kinetics of the internal contamination, increasing the acute effects beyond those anticipated. As a result, we believe that a combined exposure poses a unique challenge to the medical community during both the acute and, possibly, delayed recovery stages.
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http://dx.doi.org/10.1080/09553002.2019.1644932DOI Listing
November 2019

Aged marrow macrophages expand platelet-biased hematopoietic stem cells via Interleukin1B.

JCI Insight 2019 04 18;5. Epub 2019 Apr 18.

Department of Medicine.

The bone marrow microenvironment (BMME) contributes to the regulation of hematopoietic stem cell (HSC) function, though its role in age-associated lineage skewing is poorly understood. Here we show that dysfunction of aged marrow macrophages (Mφs) directs HSC platelet-bias. Mφs from the marrow of aged mice and humans exhibited an activated phenotype, with increased expression of inflammatory signals. Aged marrow Mφs also displayed decreased phagocytic function. Senescent neutrophils, typically cleared by marrow Mφs, were markedly increased in aged mice, consistent with functional defects in Mφ phagocytosis and efferocytosis. In aged mice, Interleukin 1B (IL1B) was elevated in the bone marrow and caspase 1 activity, which can process pro-IL1B, was increased in marrow Mφs and neutrophils. Mechanistically, IL1B signaling was necessary and sufficient to induce a platelet bias in HSCs. In young mice, depletion of phagocytic cell populations or loss of the efferocytic receptor Axl expanded platelet-biased HSCs. Our data support a model wherein increased inflammatory signals and decreased phagocytic function of aged marrow Mφs induce the acquisition of platelet bias in aged HSCs. This work highlights the instructive role of Mφs and IL1B in the age-associated lineage-skewing of HSCs, and reveals the therapeutic potential of their manipulation as antigeronic targets.
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http://dx.doi.org/10.1172/jci.insight.124213DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6542605PMC
April 2019

EVI1 overexpression reprograms hematopoiesis via upregulation of Spi1 transcription.

Nat Commun 2018 10 12;9(1):4239. Epub 2018 Oct 12.

Department of Pathology and Laboratory Medicine, University of Rochester Medical Center, Rochester, NY, 14642, USA.

Inv(3q26) and t(3:3)(q21;q26) are specific to poor-prognosis myeloid malignancies, and result in marked overexpression of EVI1, a zinc-finger transcription factor and myeloid-specific oncoprotein. Despite extensive study, the mechanism by which EVI1 contributes to myeloid malignancy remains unclear. Here we describe a new mouse model that mimics the transcriptional effects of 3q26 rearrangement. We show that EVI1 overexpression causes global distortion of hematopoiesis, with suppression of erythropoiesis and lymphopoiesis, and marked premalignant expansion of myelopoiesis that eventually results in leukemic transformation. We show that myeloid skewing is dependent on DNA binding by EVI1, which upregulates Spi1, encoding master myeloid regulator PU.1. We show that EVI1 binds to the -14 kb upstream regulatory element (-14kbURE) at Spi1; knockdown of Spi1 dampens the myeloid skewing. Furthermore, deletion of the -14kbURE at Spi1 abrogates the effects of EVI1 on hematopoietic stem cells. These findings support a novel mechanism of leukemogenesis through EVI1 overexpression.
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http://dx.doi.org/10.1038/s41467-018-06208-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6185954PMC
October 2018

The Chemokine CCL3 Regulates Myeloid Differentiation and Hematopoietic Stem Cell Numbers.

Sci Rep 2018 10 2;8(1):14691. Epub 2018 Oct 2.

Department of Medicine Hematology/Oncology Division University of Rochester School of Medicine and Dentistry, Rochester, NY, USA.

The chemokine CCL3 is frequently overexpressed in malignancies and overexpression leads to microenvironmental dysfunction. In murine models of chronic myelogenous leukemia (CML), CCL3 is critical for the maintenance of a leukemia stem cell population, and leukemia progression. With CCL3 implicated as a potentially viable therapeutic target, it is important to carefully characterize its role in normal hematopoietic homeostasis. CCL3 mice were used to evaluate the role of CCL3 in regulating hematopoietic stem and progenitor cell (HSPC) populations. CCL3 mice had loss of mature myeloid populations, while myeloid progenitors and HSPCs were increased, and microenvironmental populations were unchanged. These data show that CCL3 promotes myeloid lineage differentiation and the size of the HSPC pool independent of the supportive bone marrow microenvironment. Our results demonstrate a previously unrecognized role of CCL3 in the maintenance of homeostatic hematopoiesis that should be evaluated when targeting CCL3 signaling for the treatment of hematologic malignancy.
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http://dx.doi.org/10.1038/s41598-018-32978-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6168534PMC
October 2018

The hematopoietic stem cell niche: What's so special about bone?

Bone 2019 02 17;119:8-12. Epub 2018 May 17.

Department of Medicine Hematology/Oncology Division, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA; Wilmot Cancer Institute, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA; Center for Musculoskeletal Research, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA. Electronic address:

Hematopoietic stem cells (HSCs) require a supportive microenvironment to regulate their function and produce sufficient hematopoietic cells over the lifetime of an individual. With the exception of fish, all vertebrates, including mammals, maintain HSCs in a complex niche within the bone marrow. Several bone specific cellular populations have been implicated as components of the HSC niche and are part of a complex network that regulates HSC functions. However, the full extent of interactions within the HSC niche, and the role of individual cell populations remain to be fully elucidated. Further, it is not clear why fish are the exception, and what advantage is gained by housing HSCs in the bone marrow. To gain a better understanding of hematopoiesis and the mechanisms that drive hematopoietic disease processes a clearer picture of the complex HSC regulatory interactions in the bone marrow microenvironment is required.
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http://dx.doi.org/10.1016/j.bone.2018.05.017DOI Listing
February 2019

Anticancer activity profiling of parthenolide analogs generated via P450-mediated chemoenzymatic synthesis.

Bioorg Med Chem 2018 04 8;26(7):1365-1373. Epub 2017 Aug 8.

Department of Chemistry, University of Rochester, Rochester, NY 14627, United States. Electronic address:

The plant-derived sesquiterpene lactone parthenolide (PTL) was recently found to possess promising anticancer activity but elaboration of this natural product scaffold for optimization of its pharmacological properties has proven challenging via available chemical methods. In this work, P450-catalyzed C-H hydroxylation of positions C9 and C14 in PTL was coupled to carbamoylation chemistry to yield a panel of novel carbamate-based PTL analogs ('parthenologs'). These compounds, along with a series of other C9- and C14-functionalized parthenologs obtained via O-H acylation, alkylation, and metal-catalyzed carbene insertion, were profiled for their cytotoxicity against a diverse panel of human cancer cell lines. These studies led to the discovery of several parthenologs with significantly improved anticancer activity (2-14-fold) compared to the parent molecule. Most interestingly, two PTL analogs with high cytotoxicity (LC∼1-3μM) against T cell leukemia (Jurkat), mantle cell lymphoma (JeKo-1), and adenocarcinoma (HeLa) cells as well as a carbamate derivative with potent activity (LC=0.6μM) against neuroblastoma cells (SK-N-MC) were obtained. In addition, these analyses resulted in the identification of parthenologs featuring both a broad spectrum and tumor cell-specific anticancer activity profile, thus providing valuable probes for the future investigation of biomolecular targets that can affect cell viability across multiple as well as specific types of human cancers. Altogether, these results highlight the potential of P450-mediated chemoenzymatic C-H functionalization toward tuning and improving the anticancer activity of the natural product parthenolide.
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http://dx.doi.org/10.1016/j.bmc.2017.08.009DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5803483PMC
April 2018

The Notch Ligand Jagged1 Regulates the Osteoblastic Lineage by Maintaining the Osteoprogenitor Pool.

J Bone Miner Res 2017 Jun 9;32(6):1320-1331. Epub 2017 Mar 9.

Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA.

Notch signaling is critical for osteoblastic differentiation; however, the specific contribution of individual Notch ligands is unknown. Parathyroid hormone (PTH) regulates the Notch ligand Jagged1 in osteoblastic cells. To determine if osteolineage Jagged1 contributes to bone homeostasis, selective deletion of Jagged1 in osteolineage cells was achieved through the presence of Prx1 promoter-driven Cre recombinase expression, targeting mesenchymal stem cells (MSCs) and their progeny (PJag1 mice). PJag1 mice were viable and fertile and did not exhibit any skeletal abnormalities at 2 weeks of age. At 2 months of age, however, PJag1 mice had increased trabecular bone mass compared to wild-type (WT) littermates. Dynamic histomorphometric analysis showed increased osteoblastic activity and increased mineral apposition rate. Immunohistochemical analysis showed increased numbers of osteocalcin-positive mature osteoblasts in PJag1 mice. Also increased phenotypically defined Lin /CD45 /CD31 /Sca1 /CD51 osteoblastic cells were measured by flow cytometric analysis. Surprisingly, phenotypically defined Lin /CD45 /CD31 /Sca1 /CD51 MSCs were unchanged in PJag1 mice as measured by flow cytometric analysis. However, functional osteoprogenitor (OP) cell frequency, measured by Von Kossa colony formation, was decreased, suggesting that osteolineage Jagged1 contributes to maintenance of the OP pool. The trabecular bone increases were not due to osteoclastic defects, because PJag1 mice had increased bone resorption. Because PTH increases osteoblastic Jagged1, we sought to understand if osteolineage Jagged1 modulates PTH-mediated bone anabolism. Intermittent PTH treatment resulted in a significantly greater increase in BV/TV in PJag1 hind limbs compared to WT. These findings demonstrate a critical role of osteolineage Jagged1 in bone homeostasis, where Jagged1 maintains the transition of OP to maturing osteoblasts. This novel role of Jagged1 not only identifies a regulatory loop maintaining appropriate populations of osteolineage cells, but also provides a novel approach to increase trabecular bone mass, particularly in combination with PTH, through modulation of Jagged1. © 2017 American Society for Bone and Mineral Research.
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http://dx.doi.org/10.1002/jbmr.3106DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5466455PMC
June 2017

Targeting of the bone marrow microenvironment improves outcome in a murine model of myelodysplastic syndrome.

Blood 2016 Feb 4;127(5):616-25. Epub 2015 Dec 4.

Division of Endocrinology and Metabolism, Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY.

In vitro evidence suggests that the bone marrow microenvironment (BMME) is altered in myelodysplastic syndromes (MDSs). Here, we study the BMME in MDS in vivo using a transgenic murine model of MDS with hematopoietic expression of the translocation product NUP98-HOXD13 (NHD13). This model exhibits a prolonged period of cytopenias prior to transformation to leukemia and is therefore ideal to interrogate the role of the BMME in MDS. In this model, hematopoietic stem and progenitor cells (HSPCs) were decreased in NHD13 mice by flow cytometric analysis. The reduction in the total phenotypic HSPC pool in NHD13 mice was confirmed functionally with transplantation assays. Marrow microenvironmental cellular components of the NHD13 BMME were found to be abnormal, including increases in endothelial cells and in dysfunctional mesenchymal and osteoblastic populations, whereas megakaryocytes were decreased. Both CC chemokine ligand 3 and vascular endothelial growth factor, previously shown to be increased in human MDS, were increased in NHD13 mice. To assess whether the BMME contributes to disease progression in NHD13 mice, we performed transplantation of NHD13 marrow into NHD13 mice or their wild-type (WT) littermates. WT recipients as compared with NHD13 recipients of NHD13 marrow had a lower rate of the combined outcome of progression to leukemia and death. Moreover, hematopoietic function was superior in a WT BMME as compared with an NHD13 BMME. Our data therefore demonstrate a contributory role of the BMME to disease progression in MDS and support a therapeutic strategy whereby manipulation of the MDS microenvironment may improve hematopoietic function and overall survival.
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http://dx.doi.org/10.1182/blood-2015-06-653113DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4742549PMC
February 2016

Osteoblasts as leukemia-initiating cells.

Bonekey Rep 2014 3;3:572. Epub 2014 Sep 3.

Department of Medicine, University of Rochester School of Medicine and Dentistry , Rochester NY, USA ; Center for Musculoskeletal Research, University of Rochester School of Medicine and Dentistry , Rochester NY, USA ; Wilmot Cancer Institute, University of Rochester School of Medicine and Dentistry , Rochester NY, USA ; Endocrine Division, University of Rochester School of Medicine and Dentistry , Rochester NY, USA.

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http://dx.doi.org/10.1038/bonekey.2014.67DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4162463PMC
September 2014

Hematopoietic stem cell cultures and assays.

Methods Mol Biol 2014 ;1130:315-324

University of Rochester Medical Center, Rochester, NY, USA.

The adult hematopoietic system is repopulated in its entirety from a rare cell type known as hematopoietic stem cells (HSCs) that reside in the marrow space throughout the skeletal system. Here we describe the isolation and identification of HSCs both phenotypically and functionally.
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http://dx.doi.org/10.1007/978-1-62703-989-5_24DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4419375PMC
September 2014

Prostaglandin E2 increases hematopoietic stem cell survival and accelerates hematopoietic recovery after radiation injury.

Stem Cells 2013 Feb;31(2):372-83

Department of Medicine, University of Rochester School of Medicine, Rochester, NY 14642, USA.

Hematopoietic stem and progenitor cells (HSPCs), which continuously maintain all mature blood cells, are regulated within the marrow microenvironment. We previously reported that pharmacologic treatment of naïve mice with prostaglandin E2 (PGE2) expands HSPCs. However, the cellular mechanisms mediating this expansion remain unknown. Here, we demonstrate that PGE2 treatment in naïve mice inhibits apoptosis of HSPCs without changing their proliferation rate. In a murine model of sublethal total body irradiation (TBI), in which HSPCs are rapidly lost, treatment with a long-acting PGE2 analog (dmPGE2) reversed the apoptotic program initiated by TBI. dmPGE2 treatment in vivo decreased the loss of functional HSPCs following radiation injury, as demonstrated both phenotypically and by their increased reconstitution capacity. The antiapoptotic effect of dmPGE2 on HSPCs did not impair their ability to differentiate in vivo, resulting instead in improved hematopoietic recovery after TBI. dmPGE2 also increased microenvironmental cyclooxygenase-2 expression and expanded the α-smooth muscle actin-expressing subset of marrow macrophages, thus enhancing the bone marrow microenvironmental response to TBI. Therefore, in vivo treatment with PGE2 analogs may be particularly beneficial to HSPCs in the setting of injury by targeting them both directly and also through their niche. The current data provide rationale for in vivo manipulation of the HSPC pool as a strategy to improve recovery after myelosuppression.
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http://dx.doi.org/10.1002/stem.1286DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3580384PMC
February 2013

Bone marrow-derived matrix metalloproteinase-9 is associated with fibrous adhesion formation after murine flexor tendon injury.

PLoS One 2012 11;7(7):e40602. Epub 2012 Jul 11.

Center for Musculoskeletal Research, University of Rochester, Rochester, New York, United States of America.

The pathogenesis of adhesions following primary tendon repair is poorly understood, but is thought to involve dysregulation of matrix metalloproteinases (Mmps). We have previously demonstrated that Mmp9 gene expression is increased during the inflammatory phase following murine flexor digitorum (FDL) tendon repair in association with increased adhesions. To further investigate the role of Mmp9, the cellular, molecular, and biomechanical features of healing were examined in WT and Mmp9(-/-) mice using the FDL tendon repair model. Adhesions persisted in WT, but were reduced in Mmp9(-/-) mice by 21 days without any decrease in strength. Deletion of Mmp9 resulted in accelerated expression of neo-tendon associated genes, Gdf5 and Smad8, and delayed expression of collagen I and collagen III. Furthermore, WT bone marrow cells (GFP(+)) migrated specifically to the tendon repair site. Transplanting myeloablated Mmp9(-/-) mice with WT marrow cells resulted in greater adhesions than observed in Mmp9(-/-) mice and similar to those seen in WT mice. These studies show that Mmp9 is primarily derived from bone marrow cells that migrate to the repair site, and mediates adhesion formation in injured tendons. Mmp9 is a potential target to limit adhesion formation in tendon healing.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0040602PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3394706PMC
January 2013

Osteoblastic N-cadherin is not required for microenvironmental support and regulation of hematopoietic stem and progenitor cells.

Blood 2012 Jul 17;120(2):303-13. Epub 2012 May 17.

Endocrine Division, Department of Medicine, University of Rochester School of Medicine, 601 Elmwood Ave, Rochester, NY 14642, USA.

Hematopoietic stem cell (HSC) regulation is highly dependent on interactions with the marrow microenvironment. Controversy exists on N-cadherin's role in support of HSCs. Specifically, it is unknown whether microenvironmental N-cadherin is required for normal marrow microarchitecture and for hematopoiesis. To determine whether osteoblastic N-cadherin is required for HSC regulation, we used a genetic murine model in which deletion of Cdh2, the gene encoding N-cadherin, has been targeted to cells of the osteoblastic lineage. Targeted deletion of N-cadherin resulted in an age-dependent bone phenotype, ultimately characterized by decreased mineralized bone, but no difference in steady-state HSC numbers or function at any time tested, and normal recovery from myeloablative injury. Intermittent parathyroid hormone (PTH) treatment is well established as anabolic to bone and to increase marrow HSCs through microenvironmental interactions. Lack of osteoblastic N-cadherin did not block the bone anabolic or the HSC effects of PTH treatment. This report demonstrates that osteoblastic N-cadherin is not required for regulation of steady-state hematopoiesis, HSC response to myeloablation, or for rapid expansion of HSCs through intermittent treatment with PTH.
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http://dx.doi.org/10.1182/blood-2011-09-377853DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3398755PMC
July 2012

Osteoblastic expansion induced by parathyroid hormone receptor signaling in murine osteocytes is not sufficient to increase hematopoietic stem cells.

Blood 2012 Mar 18;119(11):2489-99. Epub 2012 Jan 18.

Department of Medicine, Division of Endocrinology, and J. P. Wilmot Cancer Center, University of Rochester School of Medicine, Rochester, NY 14642, USA.

Microenvironmental expansion of hematopoietic stem cells (HSCs) is induced by treatment with parathyroid hormone (PTH) or activation of the PTH receptor (PTH1R) in osteoblastic cells; however, the osteoblastic subset mediating this action of PTH is unknown. Osteocytes are terminally differentiated osteoblasts embedded in mineralized bone matrix but are connected with the BM. Activation of PTH1R in osteocytes increases osteoblastic number and bone mass. To establish whether osteocyte-mediated PTH1R signaling expands HSCs, we studied mice expressing a constitutively active PTH1R in osteocytes (TG mice). Osteoblasts, osteoclasts, and trabecular bone were increased in TG mice without changes in BM phenotypic HSCs or HSC function. TG mice had progressively increased trabecular bone but decreased HSC function. In severely affected TG mice, phenotypic HSCs were decreased in the BM but increased in the spleen. TG osteocytes had no increase in signals associated with microenvironmental HSC support, and the spindle-shaped osteoblastic cells that increased with PTH treatment were not present in TG bones. These findings demonstrate that activation of PTH1R signaling in osteocytes does not expand BM HSCs, which are instead decreased in TG mice. Therefore, osteocytes do not mediate the HSC expansion induced by PTH1R signaling. Further, osteoblastic expansion is not sufficient to increase HSCs.
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http://dx.doi.org/10.1182/blood-2011-06-360933DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3311272PMC
March 2012

Functional inhibition of osteoblastic cells in an in vivo mouse model of myeloid leukemia.

Blood 2012 Jan 28;119(2):540-50. Epub 2011 Sep 28.

Endocrine Metabolism Division, University of Rochester School of Medicine and Dentistry, NY 14642, USA.

Pancytopenia is a major cause of morbidity in acute myeloid leukemia (AML), yet its cause is unclear. Normal osteoblastic cells have been shown to support hematopoiesis. To define the effects of leukemia on osteoblastic cells, we used an immunocompetent murine model of AML. Leukemic mice had inhibition of osteoblastic cells, with decreased serum levels of the bone formation marker osteocalcin. Osteoprogenitor cells and endosteal-lining osteopontin(+) cells were reduced, and osteocalcin mRNA in CD45(-) marrow cells was diminished. This resulted in severe loss of mineralized bone. Osteoclasts were only transiently increased without significant increases in bone resorption, and their inhibition only partially rescued leukemia-induced bone loss. In vitro data suggested that a leukemia-derived secreted factor inhibited osteoblastic cells. Because the chemokine CCL-3 was recently reported to inhibit osteoblastic function in myeloma, we tested its expression in our model and in AML patients. Consistent with its potential novel role in leukemic-dependent bone loss, CCL-3 mRNA was significantly increased in malignant marrow cells from leukemic mice and from samples from AML patients. Based on these results, we propose that therapeutic mitigation of leukemia-induced uncoupling of osteoblastic and osteoclastic cells may represent a novel approach to promote normal hematopoiesis in patients with myeloid neoplasms.
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http://dx.doi.org/10.1182/blood-2011-04-348151DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3384480PMC
January 2012

In vivo prostaglandin E2 treatment alters the bone marrow microenvironment and preferentially expands short-term hematopoietic stem cells.

Blood 2009 Nov 2;114(19):4054-63. Epub 2009 Sep 2.

Endocrine Division, University of Rochester School of Medicine, Rochester, NY 14642, USA.

Microenvironmental signals can determine hematopoietic stem cell (HSC) fate choices both directly and through stimulation of niche cells. In the bone marrow, prostaglandin E(2) (PGE(2)) is known to affect both osteoblasts and osteoclasts, whereas in vitro it expands HSCs and affects differentiation of hematopoietic progenitors. We hypothesized that in vivo PGE(2) treatment could expand HSCs through effects on both HSCs and their microenvironment. PGE(2)-treated mice had significantly decreased number of bone trabeculae, suggesting disruption of their microarchitecture. In addition, in vivo PGE(2) increased lineage(-) Sca-1(+) c-kit(+) bone marrow cells without inhibiting their differentiation. However, detailed immunophenotyping demonstrated a PGE(2)-dependent increase in short-term HSCs/multipotent progenitors (ST-HSCs/MPPs) only. Bone marrow cells transplanted from PGE(2) versus vehicle-treated donors had superior lymphomyeloid reconstitution, which ceased by 16 weeks, also suggesting that ST-HSCs were preferentially expanded. This was confirmed by serial transplantation studies. Thus in vivo PGE(2) treatment, probably through a combination of direct and microenvironmental actions, preferentially expands ST-HSCs in the absence of marrow injury, with no negative impact on hematopoietic progenitors or long-term HSCs. These novel effects of PGE(2) could be exploited clinically to increase donor ST-HSCs, which are highly proliferative and could accelerate hematopoietic recovery after stem cell transplantation.
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http://dx.doi.org/10.1182/blood-2009-03-205823DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2774547PMC
November 2009

Hematopoietic niche and bone meet.

Curr Opin Support Palliat Care 2008 Sep;2(3):211-7

Endocrine Division, Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642, USA.

Purpose Of Review: To provide an overview of the hematopoietic stem cell (HSC) niche in the bone marrow. In addition to highlighting recent advances in the field, we will also discuss components of the niche that may contribute to the development of cancer, or cancer metastases to the bone.

Recent Findings: Much progress has been very recently made in the understanding of the cellular and molecular interactions in the HSC microenvironment. These recent findings point out the extraordinary complexity of the HSC microenvironment. Emerging data also suggest convergence of signals important for HSC and for leukemia or metastatic disease support.

Summary: The HSC niche comprises complex interactions between multiple cell types and molecules requiring cell-cell signaling as well as local secretion. These components can be thought of as therapeutic targets not only for HSC expansion, but also to modify behavior of hematopoietic malignancies and cancer metastases to the bone.
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http://dx.doi.org/10.1097/SPC.0b013e32830d5c12DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2572865PMC
September 2008

Parathyroid hormone stimulates expression of the Notch ligand Jagged1 in osteoblastic cells.

Bone 2006 Sep 2;39(3):485-93. Epub 2006 May 2.

Endocrine Division, Department of Medicine, University of Rochester School of Medicine, 601 Elmwood Avenue Box 693 Rochester, NY 14642, USA.

We previously demonstrated that activation of the Parathyroid Hormone Receptor (PTH1R) in osteoblastic cells increases the Notch ligand Jagged1 and expands hematopoietic stem cells (HSC) through Notch signaling. However, regulation of Jagged1 by PTH in osteoblasts is poorly understood. The present study demonstrates that PTH treatment increases Jagged1 levels in a subpopulation of osteoblastic cells in vivo and in UMR106 osteoblastic cells in vitro. Since PTH(1-34) activates both Adenylate Cyclase/Protein Kinase A (AC/PKA) and Protein Kinase C (PKC) downstream of the PTH1R in osteoblastic cells, we independently determined the effect of either pathway on Jagged1. Activation of AC with Forskolin or PKA with PTH(1-31) or cell-permeable cAMP analogues increased osteoblastic Jagged1. This PTH-dependent Jagged1 increase was blocked by H89 and PKI, specific PKA inhibitors. In contrast, PKC activation with phorbol ester (PMA) or PTH(13-34) did not stimulate Jagged1 expression, and PTH-dependent Jagged1 stimulation was not blocked by Gö6976, a conventional PKC inhibitor. Therefore, PTH treatment stimulates osteoblastic Jagged1 mainly through the AC/PKA signaling pathway downstream of the PTH1R. Since Jagged1/Notch signaling has been implicated not only in stromal-HSC interactions but also in osteoblastic differentiation, Jagged1 may play a critical role in mediating the PTH-dependent expansion of HSC, as well as the anabolic effect of PTH in bone.
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http://dx.doi.org/10.1016/j.bone.2006.03.002DOI Listing
September 2006